Method and apparatus for improving beam finding in a wireless communication system

ABSTRACT

A method and apparatus for improving beam finding in a wireless communication system. In one embodiment, the method includes the base station detecting a first preamble transmission from a UE on a beam. The method also includes the base station examining extra transmissions to detect whether there are other beams which can be used to communicate with the UE. The method further includes the base station considering a beam set of the UE is complete if a rule is fulfilled, wherein the beam set of the UE includes beam(s) through which the UE could communicate with the base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/005,540, filed on Jan. 25, 2016, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/107,937 filed on Jan. 26,2015, and U.S. Provisional Patent Application Ser. No. 62/107,945 filedon Jan. 26, 2015, the entire disclosures of which are incorporatedherein in their entirety by reference.

FIELD

This disclosure generally relates to wireless communication networks,and more particularly, to a method and apparatus for improving beamfinding in a wireless communication system.

BACKGROUND

With the rapid rise in demand for communication of large amounts of datato and from mobile communication devices, traditional mobile voicecommunication networks are evolving into networks that communicate withInternet Protocol (IP) data packets. Such IP data packet communicationcan provide users of mobile communication devices with voice over IP,multimedia, multicast and on-demand communication services.

An exemplary network structure for which standardization is currentlytaking place is an Evolved Universal Terrestrial Radio Access Network(E-UTRAN). The E-UTRAN system can provide high data throughput in orderto realize the above-noted voice over IP and multimedia services. TheE-UTRAN system's standardization work is currently being performed bythe 3GPP standards organization. Accordingly, changes to the currentbody of 3GPP standard are currently being submitted and considered toevolve and finalize the 3GPP standard.

Furthermore, EU started the METIS project in November 2012 to lay thefoundation of 5G, the next generation mobile and wireless communicationssystem. The main technical objectives (or 5G requirements) include thefollowing:

-   -   1000 times higher mobile data volume per area;    -   10 to 100 times higher number of connected devices;    -   10 to 100 times higher user data rate;    -   10 times longer battery life for low power massive machine        communications (MMC); and    -   5 times reduced End-to-End latency (<5 ms).

It is clear the above requirements demand much higher system capacitythan what can be offered by the legacy systems. Thus, a new radio accesstechnology can be expected to fulfill these requirements.

SUMMARY

A method and apparatus for improving beam finding in a wirelesscommunication system. In one embodiment, the method includes the basestation detecting a first preamble transmission from a UE on a beam. Themethod also includes the base station examining extra transmissions todetect whether there are other beams which can be used to communicatewith the UE. The method further includes the base station considering abeam set of the UE is complete if a rule is fulfilled, wherein the beamset of the UE includes beam(s) through which the UE could communicatewith the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a wireless communication system according toone exemplary embodiment.

FIG. 2 is a block diagram of a transmitter system (also known as accessnetwork) and a receiver system (also known as user equipment or UE)according to one exemplary embodiment.

FIG. 3 is a functional block diagram of a communication system accordingto one exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3according to one exemplary embodiment.

FIG. 5 illustrates a contention-based Random Access procedure.

FIG. 6 illustrates a contention-free Random Access procedure.

FIG. 7 illustrates a first strategy according to one exemplaryembodiment to determine whether a beam set of a UE is complete or a beamfinding procedure is finished.

FIG. 8 illustrates a second strategy according to one exemplaryembodiment to determine whether a beam set of a UE is complete or a beamfinding procedure is finished.

FIG. 9 illustrates a third strategy according to one exemplaryembodiment to determine whether a beam set of a UE is complete or a beamfinding procedure is finished.

FIG. 10 is a flow chart according to one exemplary embodiment.

FIG. 11 is a flow chart according to one exemplary embodiment.

FIG. 12 is a flow chart according to one exemplary embodiment.

FIG. 13 is a flow chart according to one exemplary embodiment.

DETAILED DESCRIPTION

The exemplary wireless communication systems and devices described belowemploy a wireless communication system, supporting a broadcast service.Wireless communication systems are widely deployed to provide varioustypes of communication such as voice, data, and so on. These systems maybe based on code division multiple access (CDMA), time division multipleaccess (TDMA), orthogonal frequency division multiple access (OFDMA),3GPP LTE (Long Term Evolution) wireless access, 3GPP LTE-A orLTE-Advanced (Long Term Evolution Advanced), 3GPP2 UMB (Ultra MobileBroadband), WiMax, or some other modulation techniques.

In particular, the exemplary wireless communication systems devicesdescribed below may be designed to support the wireless technologydiscussed in the various documents, including: “DOCOMO 5G White Paper”by NTT Docomo, Inc. Furthermore, the exemplary wireless communicationsystems devices described below may be designed to support one or morestandards such as the standard offered by a consortium named “3rdGeneration Partnership Project” referred to herein as 3GPP, including:R2-145410, “Introduction of Dual Connectivity”, NTT Docomo, Inc., NEC;TS 36.321 V12.3.0, “E-UTRA MAC protocol specification”; and TS 36.213V12.3.0, “E-UTRA Physical layer procedures”. The standards and documentslisted above are hereby expressly incorporated by reference in theirentirety.

FIG. 1 shows a multiple access wireless communication system accordingto one embodiment of the invention. An access network 100 (AN) includesmultiple antenna groups, one including 104 and 106, another including108 and 110, and an additional including 112 and 114. In FIG. 1, onlytwo antennas are shown for each antenna group, however, more or fewerantennas may be utilized for each antenna group. Access terminal 116(AT) is in communication with antennas 112 and 114, where antennas 112and 114 transmit information to access terminal 116 over forward link120 and receive information from access terminal 116 over reverse link118. Access terminal (AT) 122 is in communication with antennas 106 and108, where antennas 106 and 108 transmit information to access terminal(AT) 122 over forward link 126 and receive information from accessterminal (AT) 122 over reverse link 124. In a FDD system, communicationlinks 118, 120, 124 and 126 may use different frequency forcommunication. For example, forward link 120 may use a differentfrequency then that used by reverse link 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access network. Inthe embodiment, antenna groups each are designed to communicate toaccess terminals in a sector of the areas covered by access network 100.

In communication over forward links 120 and 126, the transmittingantennas of access network 100 may utilize beamforming in order toimprove the signal-to-noise ratio of forward links for the differentaccess terminals 116 and 122. Also, an access network using beamformingto transmit to access terminals scattered randomly through its coveragecauses less interference to access terminals in neighboring cells thanan access network transmitting through a single antenna to all itsaccess terminals.

An access network (AN) may be a fixed station or base station used forcommunicating with the terminals and may also be referred to as anaccess point, a Node B, a base station, an enhanced base station, anevolved Node B (eNB), or some other terminology. An access terminal (AT)may also be called user equipment (UE), a wireless communication device,terminal, access terminal or some other terminology.

FIG. 2 is a simplified block diagram of an embodiment of a transmittersystem 210 (also known as the access network) and a receiver system 250(also known as access terminal (AT) or user equipment (UE)) in a MIMOsystem 200. At the transmitter system 210, traffic data for a number ofdata streams is provided from a data source 212 to a transmit (TX) dataprocessor 214.

In one embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 214 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain embodiments, TX MIMO processor 220 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 260 is complementary to thatperformed by TX MIMO processor 220 and TX data processor 214 attransmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use(discussed below). Processor 270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams from a datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250. Processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights then processes the extractedmessage.

Turning to FIG. 3, this figure shows an alternative simplifiedfunctional block diagram of a communication device according to oneembodiment of the invention. As shown in FIG. 3, the communicationdevice 300 in a wireless communication system can be utilized forrealizing the UEs (or ATs) 116 and 122 in FIG. 1, and the wirelesscommunications system is preferably the LTE system. The communicationdevice 300 may include an input device 302, an output device 304, acontrol circuit 306, a central processing unit (CPU) 308, a memory 310,a program code 312, and a transceiver 314. The control circuit 306executes the program code 312 in the memory 310 through the CPU 308,thereby controlling an operation of the communications device 300. Thecommunications device 300 can receive signals input by a user throughthe input device 302, such as a keyboard or keypad, and can outputimages and sounds through the output device 304, such as a monitor orspeakers. The transceiver 314 is used to receive and transmit wirelesssignals, delivering received signals to the control circuit 306, andoutputting signals generated by the control circuit 306 wirelessly. Thecommunication device 300 in a wireless communication system can also beutilized for realizing the AN 100 in FIG. 1.

FIG. 4 is a simplified block diagram of the program code 312 shown inFIG. 3 in accordance with one embodiment of the invention. In thisembodiment, the program code 312 includes an application layer 400, aLayer 3 portion 402, and a Layer 2 portion 404, and is coupled to aLayer 1 portion 406. The Layer 3 portion 402 generally performs radioresource control. The Layer 2 portion 404 generally performs linkcontrol. The Layer 1 portion 406 generally performs physicalconnections.

The DOCOMO 5G White Paper introduces a 5G radio access concept thatefficiently integrates both lower and higher frequency bands. Sincehigher frequency bands provide opportunities for wider spectrum but havecoverage limitations because of higher path loss, it was proposed that a5G system has a two-layer structure which consists of a coverage layer(e.g., consisting of macro cells) and a capacity layer (e.g., consistingof small cells or phantom cells). The coverage layer uses existing lowerfrequency bands to provide basic coverage and mobility. The capacitylayer uses new higher frequency bands to provide high data ratetransmission. The coverage layer could be supported by enhanced LTE RAT(Long Term Evolution Radio Access Technology), while the capacity layercould be supported by a new RAT dedicated to higher frequency bands.Furthermore, integration of the coverage and capacity layers is enabledby the tight interworking (e.g., dual connectivity) between the enhancedLTE RAT and the new RAT.

Dual connectivity is a mode of operation for a UE (User Equipment) inRRC_CONNECTED, configured with a Master Cell Group and a Secondary CellGroup as discussed in 3GPP R2-145410. A Master Cell Group is a group ofserving cells associated with the MeNB (Master Evolved Node B),comprising of the PCell (Primary Cell) and optionally one or more SCell(Secondary Cell). A Secondary Cell Group is a group of serving cellsassociated with the SeNB (Secondary Evolved Node B), comprising of aSpCell (Special Cell) and optionally one or more SCell (Secondary Cell).A UE configured with dual connectivity generally means that the UE isconfigured to utilize radio resources that are provided by two distinctschedulers, and located in two eNBs (MeNB and SeNB) connected via anon-ideal backhaul over the X2 interface. Furthermore, C-plane messagesare communicated via MeNB. Further details of dual connectivity can befound in 3GPP R2-145410.

In dual connectivity, a random access (RA) procedure may be performedupon SCG (Secondary Cell Group) addition/modification if instructed,upon DL (downlink) data arrival during RRC_CONNECTED requiring randomaccess procedure (e.g., when UL (uplink) synchronization status isnon-synchronised), or upon UL data arrival during RRC_CONNECTEDrequiring random access procedure (e.g., when UL synchronisation statusis non-synchronised or when there is no resource for SR (SchedulingRequest) available). A random access initiated by the UE is performedonly on PSCell for SCG.

There are two different types of RA procedures: contention-based RA andcontention-free RA. A contention based RA procedure is shown in FIG. 5and includes the following four steps:

1. Random Access Preamble is transmitted by UE on RACH (Random AccessChannel), and is mapped to PRACH (Physical Random Access Channel);2. Random Access Response is received from eNB on DL-SCH (DownlinkShared Channel), and is mapped to PDSCH (Physical Uplink SharedChannel);3. Scheduled Transmission is transmitted by UE on UL-SCH (Uplink-SharedChannel), and is mapped to PUSCH (Physical Uplink Shared Channel); and4. Contention Resolution is received from eNB on PDCCH (PhysicalDownlink Control Channel) or on DL-SCH, and is mapped to PDSCH.

A contention-free RA procedure is shown in FIG. 6 and includes thefollowing three steps:

1. Random Access Preamble assignment is received from eNB (evolved NodeB);2. Random Access Preamble is transmitted by UE on UL-SCH (Uplink-SharedChannel), and is mapped to PUSCH; and3. Random Access Response is received from eNB on DL-SCH (DownlinkShared Channel), and is mapped to PDSCH.

After transmitting a RA preamble, a UE shall monitor a PDCCH for RAresponse(s) from an eNB (i.e., a base station) in a RA response window,which starts at the subframe (or TTI (Transmission Time Interval)) thatcontains the end of the preamble transmission plus three subframes andhas length ra-ResponseWindowSize subframes, as discussed in 3GPP TS36.321 V12.3.0. If the UE does not receive a valid RA response from theeNB within the RA response window, the UE shall retransmit a RA preambleuntil the maximum number of retransmissions has been reached or a validRA response is received. Thus, it might take more than one run tocomplete a RA procedure. Details of a RA procedure can be found in 3GPPR2-145410 and TS 36.321 V12.3.0.

Furthermore, as discussed in 3GPP TS 36.213 V12.3.0, the power controlof random access procedure is properly defined to improve robustness andefficiency. The power of preamble would be increased from attempt toattempt, also known as power ramping, if the preamble attempts have notyet succeeded. In addition, once a preamble attempt succeeds, the powerlevel of that preamble attempt would be used to derive the power of thefollowing uplink transmission (e.g., PUSCH, PUCCH or reference signals).More details on this aspect can be found in 3GPP TS 36.213 V12.3.0.

Furthermore, cells on the capacity layer may use beam forming. Ingeneral, beam forming is a signal processing technique used in antennaarrays for directional signal transmission or reception. This isachieved by combining elements in a phased array in such a way thatsignals at particular angles experience constructive interference whileothers experience destructive interference. Beam forming can be used atboth the transmitting and receiving ends in order to achieve spatialselectivity. The improvement compared with omnidirectionalreception/transmission is known as the receive/transmit gain.

Beam forming is frequently applied in radar systems. The beam created bya phased array radar is comparatively narrow and highly agile comparedto a moving dish. This characteristic gives the radar the ability todetect small, fast targets like ballistic missiles in addition toaircrafts.

The benefit of co-channel interference reduction also makes beam formingattractive to a mobile communication system designer. U.S. PatentPublication No. 2010/0165914 generally discloses the concept of beamdivision multiple access (BDMA) based on beam forming technique. InBDMA, a base station can communicate with a UE via a narrow beam toobtain the receive/transmit gain. It is also possible for the basestation to communicate with a UE using multiple beams if these beams arequalified. Besides, two UEs in different beams can share the same radioresources at the same time and thus the capacity of a mobilecommunication system can increase greatly. To achieve that, the basestation should know in which beam(s) a UE can communicate with the basestation.

A beam set of a UE is generally the beam(s) through which the UE couldcommunicate with the base station. To fully utilize the benefit of BDMA(Beam Division Multiple Access), the base station has to know the beamset of the UE. One way of finding the beam set of a UE is to detectuplink transmission from that UE. For example, when UE perform a RAprocedure, eNB may detect preamble(s) from a UE on each beam to know thesignal from the UE would arrive on which beam. It is possible that notall the beams where signal can be observed from a UE would be consideredas being in the beam set of the UE. It is also possible to remove weakbeam(s) which is inefficient to use or which would cause negligibleinterference to other UE on that beam(s).

As a result, a criterion may be defined to judge whether a beam isqualified as a beam set of a UE. An example can be a beam with a signalstrength that is 20 dB lower than the signal strength of the strongestbeam of the UE would not be considered as a qualified beam, and wouldnot be included in the UE's beam set. On the other hand, a beam with asignal strength that is 15 dB lower than signal strength of thestrongest beam of the UE would be considered a qualified beam, and wouldbe included in the UE's beam set. In other words, a signal strengththreshold may be defined to determine whether a particular beam shouldbe included in the UE's beam set.

A base station or a cell may not utilize all available beams at the sametime due to hardware limitation. If there is such hardware limitation,more transmissions would be needed to scan all the beams of a cell tofind out the beam set of a UE. As an example, a cell has 9 beams intotal and can generate (transmit/receive) three beams at the same time.First, beams 1, 4, and 7 are generated. Then beams 2, 5, and 8 aregenerated. Finally, beams 3, 6, and 9 are generated. To scan all thebeams of the cell, the UE would need to conduct transmissions on threeoccasions or transmission opportunities. The followingdiscussion/solution could be applied to the case when there is suchhardware limitation as well as to the case when there is no suchhardware limitation.

When base station detects a preamble on one beam from a UE, not allqualified beam could be detected within the same attempt(s) (e.g., dueto insufficient power or channel condition on certain beam). In somecases, multiple preamble attempts with the same power level may beneeded to scan and find all the beams of a cell when the cell has alimited number of generated beams. In addition, the preamble power wouldincrease from attempt to attempt, while the current power level of thepreamble may lead to successful detection of some beam and unsuccessfuldetection of other beams. For example, stronger beams would be detectedearlier while weaker beams that qualify would not be detected. The basestation generally needs a strategy to judge or determine whether thebeam finding is finished or not. Furthermore, the UE would need toassist the base station in making such judgment or determination.

In general, to determine whether a beam set of a UE is complete or abeam finding procedure is finished, the following strategies could beconsidered independently or jointly:

Strategy 1—Once the preamble of a UE is detected on any of the beams inthe earliest attempt (i.e., the first successful preamble detection),eNB transmits RAR to finish the random access procedure, even if thebeam set may not be complete. After the random access procedure, UEwould perform some data or reference signal (RS) transmissions while thebeam set of the UE has not yet been determined and BDMA may not beapplied. The eNB would then examine the data/RS transmissions to ensure(or determine) whether there is any qualified beam whose preamble wasnot detected. The data/RS transmissions may be triggered by the RAR orby other signaling. The number of data/RS transmissions may be fixed orconfigurable. Alternatively, a signaling could be used to terminate thedata/RS transmissions to complete the beam set, and in the followingnominal data/RS transmissions are performed. After eNB examines thedata/RS transmissions and considers (or determines) that the beam set iscomplete, BDMA could then be applied. FIG. 7 illustrates an example ofStrategy 1.

Strategy 2—When the preamble of a UE is detected on any of the beams(i.e., the first successful preamble detection), eNB does not transmitcorresponding RAR. Instead, eNB continues to detect preamble to find outwhether there is any undetected qualified beam. When eNB considers (ordetermines) that the beam set is complete, eNB could send a RAR tofinish the random access procedure. BDMA could be applied afterward.FIG. 8 illustrates an example of Strategy 2.

Strategy 3—Once the preamble of a UE is detected on any of the beams inthe earliest attempt (i.e., the first successful preamble detection),eNB would transmit RAR to the UE, even if the beam set may not becomplete. The UE would then transmit several additional preambletransmissions while the beam set of the UE has not yet been determinedand BDMA may not be applied. Based on the additional preambletransmissions, eNB may be able to ensure (or determine) whether there isany qualified beam whose preamble was not detected. The preambletransmissions may be terminated by another RAR. Furthermore, the numberpreamble transmissions could be fixed or configurable. After examiningthe preamble transmissions, eNB could consider that the beam set iscomplete; and BDMA could be applied afterward. FIG. 9 illustrates anexample of Strategy 3.

In any of the three strategies, after the first successful preambledetection, several extra transmissions of preamble, data, and/or RS arerequired to allow eNB to make sure the beam set of a UE is complete.Furthermore, rules would be required for eNB to decide whether the beamset is complete.

In one embodiment, the rule could be the total number of extratransmissions. For example, after five extra transmissions, eNB wouldconsider that the beam set is complete. The qualified beam(s) detectedduring the preamble transmissions and the extra transmissions would beincluded in the beam set of the UE.

In another embodiment, the rule could the number of transmissions aftera new qualified beam is detected. For example, when a new qualified beamis detected in a preamble transmission or in an extra transmission andthere is no new qualified beam detected after three additional extratransmissions, eNB would consider that the beam set is complete. Thequalified beam detected during the preamble transmissions and the extratransmissions would be included in the beam set of the UE.

In another embodiment, the rule could be whether difference between thetransmission power of the first successful preamble detection and thetransmission power of an extra transmission exceeds a threshold. Forexample, when the difference between the transmission power of the firstsuccessful preamble detection and the transmission power of an extratransmission exceeds 20 dB, eNB would consider that the beam set iscomplete. The qualified beam(s) detected during the preambletransmissions and the extra transmissions would be included in the beamset of the UE.

In another embodiment, the rule could be when a newly detected beam isnot a qualified beam, eNB would consider that the beam set is complete.The qualified beam(s) detected during the preamble transmissions and theextra transmissions would be included in the beam set of the UE.

In another embodiment, the rule could be when the quality of a newlydetected beam is worse than certain level, eNB would consider that thebeam set is complete. For example, when the strength of a newly detectedbeam is 20 dB lower than the strongest beam, eNB would consider that thebeam set is complete. The qualified beam(s) detected during the preambletransmissions and the extra transmissions would be included in the beamset of the UE.

In general, if the cell has a limitation on the number of beams, theextra transmissions may need to be performed several times so that allthe beams of the cell could be scanned. The rules discussed in the aboveembodiments has to be fulfilled at least once.

For Strategies 1 and 3, several extra transmissions would continue afterreceiving RAR. Whether the base station could detect all the qualifiedbeams may depend on the power level of the extra transmissions.According to current power control mechanism discussed in 3GPP TS 36.213V12.3.30 (e.g., power ramping for preamble or transmission power control(TPC) command for other signals), some latency would be introduced forthe extra transmission to achieve certain power (e.g., 20 dB higher)which is not efficient.

For Strategies 1, 2, and 3, after the several extra transmission,nominal data transmission could be performed while the power level maybe higher than what is required. For example, in Strategy 2, the powerderived from the first received preamble may be sufficient for nominaldata transmission while several power rampings are performed forcompleting the beam set and several TPC commands to reduce thetransmission power are required to resume the nominal transmissionpower.

For Strategies 1 and 3, the general concept of the invention is thatafter receiving RAR, an additional power offset or larger power stepwould be taken into account for the extra transmissions. Furthermore,when the extra transmissions finish, the power would resume to thenominal level (i.e., the additional power offset/step would not be takeninto account). For Strategy 2, the general concept of the invention isto reduce the power immediately upon receiving the RAR. The base stationwould let the UE know how many additional preambles are transmittedafter the first successful preamble detection. The UE would derive powerfrom the power of the transmission of the first preamble that wasdetected on any of the beams.

In one embodiment, the UE would receive a RAR, and would transmit anextra transmission with an additional power offset. When the extratransmission finishes, the additional power offset would be reduced fromthe transmission power.

In another embodiment, a UE receives a RAR which includes the number ofadditional preambles after the first success preamble detection; and UEderives power from the power of the transmission of first preamble thatwas detected on any of the beams.

In another embodiment, there are different TPC (Transmit Power Control)command ranges in RAR for different random access procedures. Thedifferent ranges could be configured by the base station. A larger TPCcommand range could be applied for a phantom cell. Furthermore, a largerTPC command range could be applied for random access procedure for beamfinding.

FIG. 10 is a flow chart 1000 from the perspective of a base station inaccordance with one exemplary embodiment. In step 1005, the base stationdetects a first preamble transmission from a UE on a beam. In step 1010,the base station examines extra transmissions to detect whether thereare other beams which can be used to communicate with the UE. In step1015, the base station considers a beam set of the UE is complete if arule is fulfilled, wherein the beam set of the UE includes beam(s)through which the UE could communicate with the base station. In oneembodiment, the base station considers that the beam set of the UE iscomplete when all qualified beams of the UE have been found.

In one embodiment, the rule is based on a total number of extratransmissions. More specifically, the rule could be based on a number ofextra transmissions after a new qualified beam has been detected.

Alternatively, the rule could be based on a power difference between atransmission power of the first preamble and a transmission power of anextra transmission. The rule could also be based on a quality of a newlydetected beam from an extra transmission. Furthermore, the rule could bebased on whether a difference of strength of the newly detected beam andstrength of the strongest beam reaches a certain value. In addition, therule could be based on whether a newly detected beam has a quality abovea threshold.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a base station, the device 300 includes a program code 312 stored inmemory 310 of the transmitter. The CPU 308 could execute program code312 (i) to detect a first preamble transmission from a UE on a beam,(ii) to examine extra transmissions to detect whether there are otherbeams which can be used to communicate with the UE, and (iii) toconsider a beam set of the UE is complete if a rule is fulfilled,wherein the beam set of the UE includes beam(s) through which the UEcould communicate with the base station. In addition, the CPU 308 canexecute the program code 312 to perform all of the above-describedactions and steps or others described herein.

FIG. 11 is a flow chart 1100 from the perspective of a UE in accordancewith one exemplary embodiment. In step 1105, the UE transmits a preambleduring a RA procedure. In step 1110, the UE receives a RAR from a basestation after the base station detects the transmitted preamble on abeam. In step 1115, the UE performs several extra transmissions afterreceiving the RAR from the base station. In one embodiment, the numberof extra transmissions could be fixed or configurable. Furthermore, theextra transmissions could be terminated by a signaling from the basestation or by another RAR from the base station.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a UE, the device 300 includes a program code 312 stored in memory 310of the transmitter. The CPU 308 could execute program code 312 (i) totransmit a preamble during a RA procedure, (ii) to receive a RAR from abase station after the base station detects the transmitted preamble ona beam, and (iii) to perform several extra transmissions after receivingthe RAR from the base station. Furthermore, the CPU 308 can execute theprogram code 312 to perform all of the above-described actions and stepsor others described herein.

FIG. 12 is a flow chart 1200 from the perspective of a UE in accordancewith one exemplary embodiment. In step 1205, the UE transmits a firstpreamble during a RA procedure. In step 1210, the UE receives a RAR froma base station in response to the first preamble transmission after thebase station detects the first preamble on a beam. In step 1215, the UEtransmits a second preamble in response to the RAR, wherein the power ofthe second preamble transmission is the power of the first preambletransmission plus a power offset. In one embodiment, the power offset isdifferent from a ramping step.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a UE, the device 300 includes a program code 312 stored in memory 310of the transmitter. The CPU 308 could execute program code 312 (i) totransmit a first preamble during a RA procedure, (ii) to receive a RARfrom a base station in response to the first preamble transmission afterthe base station detects the first preamble on a beam, and (iii) totransmit a second preamble in response to the RAR, wherein the power ofthe second preamble transmission is the power of the first preambletransmission plus a power offset. Furthermore, the CPU 308 can executethe program code 312 to perform all of the above-described actions andsteps or others described herein.

FIG. 13 is a flow chart 1300 from the perspective of a UE in accordancewith one exemplary embodiment. In step 1305, the UE transmits a firstpreamble transmission during a random access procedure. In step 1310,the UE receives a RAR from a base station in response to the firstpreamble transmission after the base station detects the first preambleon a beam. In step 1315, the UE derives a transmission power for atransmission of a signal subsequent to the RAR. In one embodiment, theUE derives the transmission power based on ramping step informationincluded in the RAR, and the ramping step information includes how manyramping steps should be reduced to derive the transmission power.

In step 1320, the UE adds a power offset to the derived transmissionpower if the power offset is configured. In one embodiment, the poweroffset could be reduced from the derived transmission power if thesignal has been transmitted for a certain number of times. The poweroffset could also be reduced from the derived transmission power if theUE receives an indication from the base station to reduce the derivedtransmission power. In one embodiment, the power offset is applied fortransmissions for beam finding or for beam tracking, and is not appliedfor data transmissions.

In step 1325, the UE is configured with two different TPC (TransmitPower Control) command ranges in RAR, and applies the configured TPCcommand ranges to derive the transmission power for the transmission ofthe signal subsequent to the receipt of the RAR. In one embodiment, thedifferent TPC command ranges are configured for different purposes ofperforming RA procedure.

Referring back to FIGS. 3 and 4, the device 300 includes a program code312 stored in memory 310. The CPU 308 could execute program code 312 (i)to transmit a first preamble transmission during a random accessprocedure, (ii) to receive a RAR from a base station in response to thefirst preamble transmission after the base station detects the firstpreamble on a beam, and (iii) to derive a transmission power for atransmission of a signal subsequent to the RAR.

In one embodiment, the CPU 308 could further execute program code 312 toadd a power offset to the derived transmission power if the power offsetis configured. The CPU 308 could also execute program code 312 to applyconfigured TPC command ranges to derive the transmission power for thetransmission of the signal subsequent to the receipt of the RAR. Inaddition, the CPU 308 can execute the program code 312 to perform all ofthe above-described actions and steps or others described herein.

Various aspects of the disclosure have been described above. It shouldbe apparent that the teachings herein may be embodied in a wide varietyof forms and that any specific structure, function, or both beingdisclosed herein is merely representative. Based on the teachings hereinone skilled in the art should appreciate that an aspect disclosed hereinmay be implemented independently of any other aspects and that two ormore of these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. As an exampleof some of the above concepts, in some aspects concurrent channels maybe established based on pulse repetition frequencies. In some aspectsconcurrent channels may be established based on pulse position oroffsets. In some aspects concurrent channels may be established based ontime hopping sequences. In some aspects concurrent channels may beestablished based on pulse repetition frequencies, pulse positions oroffsets, and time hopping sequences.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

In addition, the various illustrative logical blocks, modules, andcircuits described in connection with the aspects disclosed herein maybe implemented within or performed by an integrated circuit (“IC”), anaccess terminal, or an access point. The IC may comprise a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, electrical components, opticalcomponents, mechanical components, or any combination thereof designedto perform the functions described herein, and may execute codes orinstructions that reside within the IC, outside of the IC, or both. Ageneral purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module (e.g., including executable instructions and relateddata) and other data may reside in a data memory such as RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of computer-readablestorage medium known in the art. A sample storage medium may be coupledto a machine such as, for example, a computer/processor (which may bereferred to herein, for convenience, as a “processor”) such theprocessor can read information (e.g., code) from and write informationto the storage medium. A sample storage medium may be integral to theprocessor. The processor and the storage medium may reside in an ASIC.The ASIC may reside in user equipment. In the alternative, the processorand the storage medium may reside as discrete components in userequipment. Moreover, in some aspects any suitable computer-programproduct may comprise a computer-readable medium comprising codesrelating to one or more of the aspects of the disclosure. In someaspects a computer program product may comprise packaging materials.

While the invention has been described in connection with variousaspects, it will be understood that the invention is capable of furthermodifications. This application is intended to cover any variations,uses or adaptation of the invention following, in general, theprinciples of the invention, and including such departures from thepresent disclosure as come within the known and customary practicewithin the art to which the invention pertains.

1. A method of a base station, comprising: the base station detects afirst preamble transmission from a UE (User Equipment) on at least onebeam; the base station transmits a Random Access Response (RAR) to theUE in response to reception of the first preamble; after transmittingthe RAR, the base station continues to examine extra transmissions ofreference signal from the UE to determine whether there are other beamswhich can be used to communicate with the UE; and the base stationconsiders a beam set of the UE is complete if a total number of extratransmissions from the UE reaches a pre-configured value, wherein thebeam set of the UE includes beam(s) through which the UE couldcommunicate with the base station.
 2. The method of claim 1, wherein thebase station considers that the beam set of the UE is complete when allbeams which can be used for communicating with the UE have been found.3. The method of claim 1, wherein a beam is included in the beam set ofthe UE if a signal strength received from the beam is greater than athreshold.
 4. A method of a UE (User Equipment), comprising: the UEtransmits a preamble during a Random Access (RA) procedure for the basestation to determine at least one beam for communicating with the UE;the UE receives a Random Access Response (RAR) from a base station aftertransmission of the preamble; and the UE performs several extratransmissions of reference signal to the base station after receivingthe RAR from the base station so that the base station could examine theextra transmissions to detect whether there are other beams which can beused to communicate with the UE.
 5. The method of claim 4, wherein atotal number of extra transmissions could be fixed or configurable. 6.The method of claim 4, wherein the UE stops the extra transmissions whena specific signaling is received from the base station.
 7. The method ofclaim 4, wherein the UE receives the RAR from the base station after thebase station detects the transmitted preamble on a beam.
 8. A UserEquipment (UE), comprising: a control circuit; a processor installed inthe control circuit; and a memory installed in the control circuit andoperatively coupled to the processor; wherein the processor isconfigured to execute a program code stored in the memory to: transmit apreamble during a Random Access (RA) procedure for the base station todetermine at least one beam for communicating with the UE; receive aRandom Access Response (RAR) from a base station after transmission ofthe preamble; and perform several extra transmissions of referencesignal to the base station after receiving the RAR from the base stationso that the base station could examine the extra transmissions to detectwhether there are other beams which can be used to communicate with theUE.
 9. The UE of claim 8, wherein a total number of extra transmissionscould be fixed or configurable.
 10. The UE of claim 8, wherein theprocessor is further configured to execute a program code stored in thememory to: stop the extra transmissions when a specific signaling isreceived from the base station.
 11. The UE of claim 8, wherein theprocessor is further configured to execute a program code stored in thememory to: receive the RAR from the base station after the base stationdetects the transmitted preamble on a beam.